Encapsulated semiconductor devices require the passage of a large current therethrough. Such an encapsulated semiconductor device has been utilized, e.g., to provide connection between a semiconductor switching element and a control circuit of an air conditioner, or to provide connection between batteries of an electric vehicle or between capacitors thereof.
FIG. 10 illustrates a schematic structure of a portion of a conventional semiconductor device described in PATENT DOCUMENT 1. As illustrated in FIG. 10, in the conventional semiconductor device, an island 21 to which a semiconductor element 24 is bonded, and an internal lead 23 are placed on a metal plate 27 for heat dissipation with a resin sheet 26 and a ceramic thin plate 28 interposed therebetween. Alumina or low-melting-point lead glass is suitable for the ceramic thin plate 28.
As such, the semiconductor device described in PATENT DOCUMENT 1 is configured such that the ceramic thin plate 28 is bonded to the back surface of the island 21 and the back surface of the internal lead 23, and furthermore, the metal plate 27 is bonded to the back surface of the ceramic thin plate 28 with the resin sheet 26 interposed therebetween. PATENT DOCUMENT 1 describes that since the semiconductor device described in PATENT DOCUMENT 1 includes the ceramic thin plate 28 between the resin sheet 26 and the island 21 or the internal lead 23, stable bonding of the internal lead 23 can be provided.
Furthermore, a semiconductor device described in PATENT DOCUMENT 2 includes a semiconductor element for power control, a metal base, and a lead frame serving as a conductor pattern. Here, the semiconductor element for power control forms a main circuit section. The metal base provides a heatsink effect for efficiently dissipating heat generated by the semiconductor element for power control to the outside. An insulative adhesion sheet is interposed between the lead frame serving as the conductor pattern and the metal base, and the lead frame serving as the conductor pattern provides connection between the semiconductor element for power control and a connecting wire.